The present invention relates to a mass flow controller which is used in, for example, a semiconductor manufacturing process.
In a semiconductor manufacturing apparatus, a mass flow controller is used for controlling a fluid such as a process gas and a liquid material. This mass flow controller provides a fluid supply system, together with filters and valves. With respect to such a fluid supply system, reduction in size and weight of the system has been desired, in order to improve performance by, for example, suppressing an escape of gas and reduce the cost of the semiconductor manufacturing apparatus.
Conventionally, components of the fluid supply system are connected by means of pipe joints. However, in order to reduce the size of the fluid supply system, it has been proposed to connect base portions of the components by a common connecting method using flanges. In this connecting method using flanges, although the size of the fluid supply system can be reduced, a fluid control system has a high component density while the weight thereof remains unchanged. Further, because many flanges are used for connecting the components, the fluid supply system becomes a metallic mass, and even the weight of the fluid supply system as a whole increases.
In the conventional connecting method using pipe joints, a base portion of the mass flow controller is produced by cutting a metal. Therefore, the mass flow controller has a large weight and is difficult to manufacture in mass production, leading to difficulty in cost reduction.
The present invention has been made, in order to solve the above-mentioned problems accompanying the conventional connecting methods with respect to the mass flow controller. It is an object of the present invention to provide a high-performance mass flow controller which is compact and lightweight, which has a fluid flow path having a simple structure and which does not have dead space in which a fluid is likely to stagnate and cause the problem of contamination.
The present invention provides a mass flow controller for controlling a mass flow rate in a predetermined range, in which a mass flow rate of a fluid is detected by a flow rate sensor and a control valve is operated so as to adjust the detected mass flow rate to a desired value. The control valve is arranged as a solenoid valve operated by means of a solenoid, and a plunger for opening and closing the solenoid valve is disposed within a cylindrical conduit having a hollow structure, whereby one-way flow of the fluid is effected in a space between an outer circumferential surface of the plunger and an inner circumferential surface of the conduit in a direction of the axis of the cylindrical conduit.
In one embodiment of the present invention, the outer circumferential surface of the plunger includes a groove extending in parallel to the axis of the conduit, to thereby provide a fluid flow path.
In another embodiment of the present invention, the plunger is made of a magnetic alloy having high anti-corrosion properties.
In a further embodiment of the present invention, the control valve comprises a spherical valve head attached to a forward end of the plunger and a valve seat corresponding to the valve head. The valve seat is arranged in a funnel-like form.
In a further embodiment of the present invention, a cylindrical yoke for guiding a magnetic flux generated by the solenoid is disposed in the conduit at a position adjacent to the plunger, which yoke is movable in the direction of the axis of the conduit, whereby an initial position of a valve head of the solenoid valve and an attractive force of an electromagnet can be adjusted by adjusting a gap between the plunger and the yoke.
In a further embodiment of the present invention, a spherical valve head is attached to one end of the plunger and a yoke having a funnel-like valve seat corresponding to the valve head is disposed adjacent to the plunger with a spring being provided therebetween, to thereby obtain a normally opened valve structure.
In a further embodiment of the present invention, a doughnut-like permanent magnet is positioned at an outer circumferential surface of the conduit at a position corresponding to the plunger, which doughnut-like permanent magnet is adjustable in terms of a position with respect to the direction of the axis of the conduit, whereby an initial axial position of the plunger when the solenoid is deenergized can be adjusted by adjusting the position of the doughnut-like permanent magnet.
In a further embodiment of the present invention, the flow rate sensor comprises a thermal mass flow rate sensor connected in parallel with the conduit.
In a further embodiment of the present invention, the flow rate sensor is arranged as a pressure based flow rate sensor. The pressure based flow rate sensor comprises a pressure gauge provided in the fluid flow path, so as to detect a pressure caused by a change in flow rate.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims taken in connection with the accompanying drawings.